Method and apparatus for providing efficient heat

ABSTRACT

Disclosed is a method for providing heat that includes preheating an incoming air flow from outside an apparatus in a first channel of a heat exchanger by a flow in a second channel of the heat exchanger, transferring the flow from the second channel outside the apparatus through an exhaust channel, providing heat by the preheated incoming air flow in a heat pump, and transferring in a transfer channel a flue gas flow provided by a burner to the second channel.

TECHNICAL FIELD

The application relates generally to a method and an apparatus for providing efficient heat.

BACKGROUND

Conventional systems for heating buildings and domestic hot water operate by means of a boiler heated with a fossil fuel, e.g. oil or gas, but those waste significantly a supplied energy due to heat losses with flue gases escaping through the chimneys of the buildings.

In order to improve an economy of such conventional systems it has been started to utilize heat pumps that raise heat of low temperature to a higher temperature level. However, when using outdoor air, an efficiency of a heat pump falls radically at low temperatures, e.g. temperatures lower than −5° C. Likewise, frost starts to deposit on the heat pump unit, whereupon it is practical to use another heat source, e.g. an oil-fired or electric boiler, in connection with the heat pump during coldest seasons.

U.S. Pat. No. 4,687,133 discloses a heating system 100 according to FIG. 1 that is developed in order to enhance a heating of buildings and domestic hot water by utilizing a combination of a heating boiler 110 and a heat pump 120.

In the heating system 100 the heat pump 120 receives an air flow that consists of a fresh air from outside a boiler room 130 and a return air entering from the boiler room 130. The air flow drift to a cross flow type heat exchanger 140 and, then, to an evaporator in the heat pump 120 for heating a heat emitting medium circulating in conduits of the heat pump 120. In a condenser the heat emitting medium heats water that runs through a water conduit so that hot water is provided for a water system of a building where the boiler room 130 is located.

The heat pump 120 exhausts the air flow to the boiler room space 130 and a part of the exhausted air flow drifts through a gas channel 150 back to the heat exchanger 140 having two separate channel systems where the incoming air flow and exhausted partial air flow travel roughly perpendicular to one another through the heat exchanger 140. The partial air flow exists from the heating system 100 via an exhaust pipe 160 after passing through the heat exchanger 140 and preheating the incoming air flow.

When there is a need for extra heating energy, e.g. during winter, the heating boiler 110 with a burner 170 is started, whereupon flue gas of oil heated by the burner 170 travels through the gas channel 150 and mixes with the partial air flow running towards the heat heat exchanger 140. The mixture including the partial air flow and the flue gas comprises now increased amount of energy when comparing to mere partial flow and that can be used for improving the activity of the heat exchanger 140.

The recognition of the need for extra heating energy and a start-up of the burner 170, as well as a management of the heating system 100 in general, are provided by means of temperature and pressure sensors 180, 182, 184, 186, 188 and a control equipment 190.

SUMMARY

One object of the invention is to improve a heating apparatus that utilizes a combination of a heating boiler and a heat pump so that it would provide heat more effectively and cleanly.

The object of the invention is fulfilled by providing a method of claim 1 and an apparatus of claim 8.

According to an embodiment of the invention a method for providing heat comprises preheating an incoming air flow from outside an apparatus in at least one first channel of a heat exchanger by means of a flow in at least one second channel of the heat exchanger, transferring the flow from the at least one second channel of the heat exchanger outside the apparatus through an exhaust channel, providing heat by means of the preheated incoming air flow in a heat pump, and transferring in a transfer channel a flue gas flow provided by a burner to the at least one second channel of the heat exchanger, the method further comprises receiving in the transfer channel a part of the exhausted flow from the exhaust channel and controlling a flow of the flue gas flow and the received part of the exhausted flow in the transfer channel so that moisture in the flue gas flow and the received part of the exhausted flow condenses on a surface of the at least one second channel of the heat exchanger and reacts with flue gas particles of the flue gas flow when the flow of the flue gas flow and the received part of the exhausted flow interacts with the incoming air flow in the at least one first channel of the heat exchanger increasing the preheating of the incoming air flow.

According to an embodiment of the invention an apparatus for providing heat comprises a heat exchanger configured to preheat an incoming air flow from outside the apparatus in at least one first channel of the heat exchanger by means of a flow in at least one second channel of the heat exchanger, an exhaust channel configuresd to transfer the flow from the at least one second channel of the heat exchanger outside the apparatus, a heat pump configured to provide heat by means of the preheated incoming air flow, and a transfer channel configured to transfer a flue gas flow provided by a burner to the at least one second channel of the heat exchanger, the apparatus further comprises the transfer channel configured to receive a part of the exhausted flow from the exhaust channel and control means configured to control a flow of the flue gas flow and the received part of the exhausted flow in the transfer channel so that moisture in the flue gas flow and the received part of the exhausted flow condenses on a surface of the at least one second channel of the heat exchanger and reacts with flue gas particles of the flue gas flow when the flow of the flue gas flow and the received part of the exhausted flow interacts with the incoming air flow in the at least one first channel of the heat exchanger increasing the preheating of the incoming air flow.

Further embodiments of the invention are defined in dependent claims.

Embodiments of the invention provides an economy of the apparatus at the same time as those ensure a function and high efficiency of the apparatus at all outdoor temperatures by increasing the preheating of the incoming air flow transferred to the heat exchanger.

In addition, embodiments of the invention improves the economy by guiding the exhausted flow from the heat exchanger partially to the return channel and enriching the preheating flow in the second channels of the heat exchanger by means of this returned partial exhausted flow so that more heat transfers from the preheating flow to the incoming flow.

Embodiments of the invention improves also the economy of the heating by enabling to stop the burner even during coldest seasons when a spontaneous process between the moisture on the channel surfaces and the flue gas particles occurs in the second channels of the heat exchanger. The process continues although the burner would be switched off, so, the process itself is capable of preheating sufficiently the incoming flow for some time and it may be necessary to start the burner until a temperature of the incoming flow falls below certain threshold temperature.

Furthermore, embodiments of the invention further improves cleaning of the second channels of the heat exchanger by means of a draining moisture on inner surfaces of the second channels and purifying flue gases exhausted from the apparatus through the exhaust channel.

The verb “to comprise” is used in this document as an open limitation that neither excludes nor requires the existence of also unrecited features. The verbs “to include” and “to have/has” are defined as to comprise.

The terms “a”, “an” and “at least one”, as used herein, are defined as one or more than one and the term “plurality” is defined as two or more than two.

The term “another”, as used herein, is defined as at least a second or more.

The term “or” is generally employed in its sense comprising “and/or” unless the content clearly dictates otherwise.

For the above-mentioned defined verbs and terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this description/specification.

Finally, the features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.

BRIEF DESCRIPTION OF THE FIGURES

Next, the preferred embodiments of the invention will be described with reference to the accompanying figures, in which

FIG. 1 illustrates an exemplary view of a heating system having a combination a heating boiler and a heat pump, and

FIG. 2 illustrates an exemplary view of an apparatus according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 has already been discussed in context of the background.

FIG. 2 illustrates a heating arrangement 200, wherein a separate heating apparatus 210 is attached to a water-carried boiler 220 with a burner 222 configured to burn e.g. oil or gas comprising hydrocarbon(s) and a tank 224 for producing hot water is connected to the boiler 220. The apparatus 210 and possibly the boiler 220 and the tank 224 are positioned on a support 230, that is e.g. a floor of a building to be heated. As one can see from the figure the apparatus 210 can be displaced in one room space and the boiler 220 another room space, but it is also possible that both locate in the same room. Only requirement relating to the displacement of the apparatus 210 is that it is displaced so that it can be connected to the chimney of the building.

The apparatus 210 comprises a heat exchanger 240, e.g. a counter current heat exchanger, that receives fresh air flow from outside the building to be heated through a channel 242 having an inlet and air flow through an internal inlet (not shown in figure). The received air flows mix and the mixed air flow from outside the apparatus 210 is guided to first channels of the heat exchanger so that it is preheated by using a preheating flow, which comprises at least flue gases and air, from the burner 222 inside second channels of the heat exchanger. The heat exchanger 240 comprises at least one first channel for the mixed air flow from the outside the apparatus 210 and at least one second channel for the preheating flow. The first and second channels having a distance less than 1 mm. Then, the preheated air flow goes to a heat pump 250, wherein it is utilized for producing heat.

The preheating flow in the second channels of the heat exchanger is guided to an exthaus chamber 244 having an exhaust fan 246 and, then, to an exhaust channel 248 a that branches to an exhaust channel 248 b leading to outside the building and a return channel 248 c leading back to the boiler 220. The exhaust channel 248 b and the return channel 248 c forms a chimney for the boiler 220 when it is used alone for some reason, e.g. because of a service or repair of the apparatus 210. The exhausted preheating flow divides so that a part of the exhausted preheating flow passes along the exhaust channel 248 b forming a upper part of the chimney outside the building and a part of the preheating flow (exhaust flow) passes along the return channel 248 c down towards the boiler 220.

The heat pump 250 that is used for heating circulating water has an internal exhaust opening 252 a with a fan for the mixed air flow that an evaporator 254 has received and utilized for providing heat. A part of the mixed air flow is transferred from inside the apparatus 210 to the room space where the apparatus 210 locates through opening 252 b. Another possible part is transferred to another room space along suitable air channel, e.g. the room where the boiler 220 locates same way. One part of the mixed air flow is filtered and it is circulated inside the apparatus towards the internal inlet for merging with the fresh air flow in the channel 242.

From the evaporator 254 a working agent flows via a heat exchanger of the heat pump 250 to a compressor provided with a pressure setter via a counter-valve to a coaxial condenser 256 for heat exchange with water in a water-carried system having inlet and discharge conduits 258 a, 258 b. From the condenser 256 the working agent flows over a receiver and a filter back to the heat exchanger of the heat pump and via a theremostat valve to the evaporator 254. A rotary blower locates in a evaporator 254 and a branch conduit leading to the evaporator 254 is controlled by a solenoid valve.

The part of the utilized and mixed air flow that is blown away through the exhaust opening 252 a and the opening 252 b to the room space outside the apparatus 210 drifts back to the apparatus 210 through an underpressure valve 260, or the boiler 220 and the burner 222.

When the burner 222 is switched on, a flue gas flow from the boiler 220 passes to a transfer channel 270, where it mixes with the exhaust flow, i.e. the part of the exhausted preheating flow, that comes down from the return channel 248 c, and, when necessary, also with the circulating air flow coming from the heat pump 250 through the underpressure valve 260.

The mixed flow that comprises the flue gases from the burner 222, the mixture comprising flue gases and air from the return channel 248 c, and, possibly, the circulating air flow coming from the room space through the underpressure valve 260 passes to a condense chamber 272 along the transfer channel 270 before it is guided to the second channels of the heat exchanger in order to preheat the air flows in the first channels of the heat exchanger. The condense chamber 272 has a condense drain 274 for guiding condensed moisture outside the apparatus 210. Air in the room space that the heat pump 250 has blown away comprises waste heat that is used by this way for improving the preheat process in the heat exchanger 240.

In the condense chamber 272 the mixed flow is near (essentially) its dew point or over the dew point, and its flow velocity is arranged to be over 3 m/s by means of the exhaust fan 246. Then, in the second channels of the heat exchanger moisture comprising e.g. water in the turbulent mixed flow condenses on inner surfaces of the second channels because of the cool fresh air and circulating air in the first channels of the heat exchanger. At the same time the condensing mixed flow preheats the air flow in the first channels.

The condensed moisture having pH about 2,5 on the inner surfaces of the second channels reacts with flue gas particles that is in the mixed air flow and that are generated by the oil or gas burner 222, and in this spontaneous process the condensed moisture binds carbon dioxide resulting dilute carbon acid having pH about 5 and resulting more heat in the second channels, whereupon heat energy that is transferred into the air flow in the first channels is added and the preheat process becomes more effective. The dilute carbon acid cleans the second channels when it drains down along the second channels e.g. back to the condense chamber 272 or other collecting chamber.

The spontaneous process between the moisture on the channel surfaces and the flue gas particles continues in the second channels although the burner would be switched off, so, the process itself is capable of preheating sufficiently the incoming flow for some time. Thus, it may be necessary to start the burner until a temperature of the incoming flow falls below certain threshold temperature.

After passing through the second channels and the preheat process, the mixed flow transfers with a help of the exhaust fan 246 to the exhaust chamber 244 and along the exhaust channel 248 a partly outside the building along the exhaust channel 248 b and partly back to the transfer channel 270 along the return channel 248 c.

According to an embodiment of the invention a method for providing heat comprises preheating an incoming air flow from outside an apparatus, i.e. one part of the incoming air flow comes from outside a room space or building to be heated and another part of the incoming air flow, a circulating air flow exhausted by the heat pump, comes from inside the apparatus, in a first channel of a heat exchanger by means of a flow in a second channel of the heat exchanger, transferring the flow from the second channel of the heat exchanger outside the apparatus through an exhaust channel, providing heat by means of the preheated incoming air flow in a heat pump, and transferring in a transfer channel a flue gas flow provided by a burner to the second channel of the heat exchanger for preheating the incoming air flow, the method further comprises receiving in the transfer channel a part of the exhausted flow from the exhaust channel and controlling a flow of the flue gas flow and the received part of the exhausted flow in the transfer channel so that moisture in the flue gas flow and the received part of the exhausted flow condenses on a inner surface of the second channel of the heat exchanger and reacts with flue gas particles of the flue gas flow when the flow of the flue gas flow and the received part of the exhausted flow interacts with the incoming air flow in the first channel of the heat exchanger increasing the preheating of the incoming air flow.

According to an embodiment of the invention an apparatus for providing heat comprises a heat exchanger configured to preheat an incoming air flow from outside the apparatus in a first channel of the heat exchanger by means of a flow in a second channel of the heat exchanger, an exhaust channel configured to transfer the flow from the second channel of the heat exchanger outside the apparatus, a heat pump configured to provide heat by means of the preheated incoming air flow, and a transfer channel configured to transfer a flue gas flow provided by a burner to the second channel of the heat exchanger, the apparatus further comprises the transfer channel configured to receive a part of the exhausted flow from the exhaust channel and control means configured to control a flow of the flue gas flow and the received part of the exhausted flow in the transfer channel so that moisture in the flue gas flow and the received part of the exhausted flow condenses on a surface of the second channel of the heat exchanger and reacts with flue gas particles of the flue gas flow when the flow of the flue gas flow and the received part of the exhausted flow interacts with the incoming air flow in the first channel of the heat exchanger increasing the preheating of the incoming air flow.

According to an embodiment of the invention the method, which is disclosed in any of the previous embodiments, further comprises mixing the flue gas flow and the received part of the exhausted flow in the transfer channel.

According to an embodiment of the invention the apparatus, which is disclosed in any of the previous embodiments, wherein the transfer channel is configured to mix the flue gas flow and the received part of the exhausted flow.

According to an embodiment of the invention the method, which is disclosed in any of the previous embodiments, further comprises providing a mixture comprising the flue gas flow and the received part of the exhausted flow in a condense chamber of the transfer channel near a dew point of the mixture comprising the flue gas flow and the received part of the exhausted flow before transferring the mixture comprising the flue gas flow and the received part of the exhausted flow into the second channel of the heat exchanger.

According to an embodiment of the invention the apparatus, which is disclosed in any of the previous embodiments, wherein the transfer channel comprises a condense chamber configured to provide a mixture comprising the flue gas flow and the received part of the exhausted flow near a dew point of the mixture comprising the flue gas flow and the received part of the exhausted flow before the mixture comprising the flue gas flow and the received part of the exhausted flow transfers into the second channel of the heat exchanger.

The flow velocity through the second channels of the heat exchanger is controlled by the exhaust fan 246, which is managed by a control unit 280 receiving information from e.g. at least one sensor (thermostat) and relay (not shown) configured to set the flow velocity and/or a flow rate of the mixed air flow when it passes through the transfer channel 270 and/or the condense chamber 272. The exhaust fan 246 controls also the flow through the first channels of the heat exchanger and, basically, all flows in the arrangement 200 by arranging low pressure inside the apparatus 210 whereupon an amount of air flow that the arrangement 200 receives depends on an amount of the exhausted flow. Optionally, a speed of the exhaust fan 246 can simply be set to a predetermined level that provides the spontaneous process in the second channels and it can be stopped in a predetermined conditions from where it can be started again when conditions are favourable. A flow velocity through the first channels can also be controlled e.g. by the fan in the internal exhaust opening 252 a, and the control unit manages the fan on the grounds of information received from e.g. at least one sensor (thermostat) and a speed control (not shown) configured to set a flow velocity and/or a flow rate of the incoming mixture flow comprising the fresh air flow from outside the building and the air flow through the internal inlet in the channel 242.

The control unit 280 manages the mixed air flow and the incoming mixture so that the mixed air flow has the flow velocity over 3 m/s in the second channels and a ratio between the mixed air flow and the incoming mixture flow is about 1 to 20 in the heat exchanger 240. Then, the mixed air flow circulating through the heat pump 250 shall surpass a quantity of the exhausted flow discharged through the exhaust channel 248 a so as to cause a higher pressure to prevail in the apparatus room than in the exhaust chamber 244.

According to an embodiment of the invention the method, which is disclosed in any of the previous embodiments, comprises preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity by means of e.g. the exhaust fan so that the heat productive reaction between the condensed moisture and the flue gas particles is possible by controlling a flow velocity of the mixture comprising the flue gas flow and the received part of the exhausted flow in the second channel of the heat exchanger.

According to an embodiment of the invention the apparatus, which is disclosed in any of the previous embodiments, wherein the control means, e.g. the control unit, are configured to control through the exhaust fan a flow velocity of the mixture comprising the flue gas flow and the received part of the exhausted flow in the second channel of the heat exchanger for preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible.

At least one of the second channels of the heat exchanger can comprise at least one tapered channel part (not shown), whereupon the draining of the condensed moisture is prevented and the spontaneous process is enabled for providing extra heat to be given away to the incoming mixture flow in the first channels of the heat exchnager.

According to an embodiment of the invention the method, which is disclosed in any of the previous embodiments, further comprises preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible by providing a tapered channel part in the second channel of the heat exchanger.

According to an embodiment of the invention the apparatus, which is disclosed in any of the previous embodiments, wherein the heat exchanger comprises a tapered channel part in the second channel of the heat exchanger for preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible.

According to an embodiment of the invention the method, which is disclosed in any of the previous embodiments, further comprises guiding the incoming air flow in the first channel of the heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flow in the second channel of the heat exchanger to flow oppositre directions in the heat exchanger by means of a counter current heat exchanger.

According to an embodiment of the invention the apparatus, which is disclosed in any of the previous embodiments, wherein the heat exchanger is a counter current heat exchanger configured to guide the incoming air flow in the first channel of the counter current heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flow in the second channel of the counter current heat exchanger to flow oppositre directions.

When the burner is switched off, eg. during warm seasons in summers, the apparatus 210, receives and mixes by means of the transfer channel 270 only the exhaust flow coming down from the return channel 248 c and the circulating air flow coming from the room space through the underpressure valve 260 for the use of the heat exchanger 240.

In order to control an operation of the apparatus 210 as well as the whole arrangement 200, when the separate apparatus 210 is attached to the boiler 220 through openings in the exhaust channel 248 b and the return channel 248 c by means of suitable connecting means and connections forming the exhaust channel 248 a and the transfer channel 270, there are temperature sensors 282 a, 282 b, 282 c, 282 d, 282 e and a pressure sensor 284 connected to a control unit 280 and configured to provide information that the control unit 280 needs for managing the operation of the apparatus 210 and the whole arrangement 200.

The boiler 220 is provided with a temperature sensor 282 a that controls starting and stopping of the burner 222 via a control relay 286, the channel 242 is provided with a temperature sensor 282 b and the apparatus 210 with an internal temperature sensor 282 c. A temperature sensor 282 d and the pressure sensor 284 are displaced in the exhaust chamber 244, and the room space where the apparatus 210 locates with a temperature sensor 282 e.

According to an embodiment of the invention the method, which is disclosed in any of the previous embodiments, wherein a control unit of the apparatus is capable of controlling an exhaust fan that is used for controlling a flow velocity of the flue gas flow as well as the flow velocity of the mixture and/or the burner of a boiler when the apparatus is connected to an exhaust channel of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of information received from at least one temperature sensor and at least one pressure sensor.

According to an embodiment of the invention the apparatus, which is disclosed in any of the previous embodiments, wherein the control means comprises a control unit configured to control an exhaust fan and/or the burner of the boiler when the apparatus is connected to an exhaust channel of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor and a pressure sensor.

When it is necessary to increase a content of the heating energy in the mixed air flow passing through the first channels of the heat exchanger 240 to the heat pump 250, e.g. during warm seasons, and when only the heat pump 250 provides the heating energy, the exhaust fan 246 is started to increase in the heat exchanger 240 the flow of both exhausted air and entering air. During a colder periods or when the outdoor temperature is otherwise low that is recognized by the temperature sensor 282 b, the burner 222 is started and the flue gases from the boiler 220 drift to the transfer channel 270 to be mixed with the exhausted flow from the return channel 248 c and the circulating air flow coming from the under-pressure valve 260, whereupon the amount of heat energy in the incoming air flow from the heat exchanger 240 to the heat pump 250 is further increased.

Following examples further describes how the arrangement 200 comprising the apparatus 210 and the boiler 220 ensures its operation under favourable conditions.

When the temperature sensor 282 a determines that a temperature is below a pre-determined temperature value, the heat pump 250 starts, and when an outdoor temperature exceeds a predetermined temperature value according to the temperature sensor 282 b, the exhaust fan 246 starts for increasing the amount of heat energy in the incoming air flow. When temperatures in the temperature sensors 282 a, 282 b, 282 c at the same time are below predetermined temperature values, the exthaus fan 246 starts, and when the pressure sensor 284 in the exhaust chamber 244 indicates that a pressure is below a predetermined pressure value, the burner 222 in the boiler 220 is started.

In addition, when a temperature in the apparatus room and/or in the apparatus 210 have exceeded predetermined temperature values according to the temperature sensors 282 d, 282 e, the burner 222 stops until the heat pump 250 and/or the exhaust fan 246 consume accumulated heat in the apparatus room and/or in the apparatus and starts again when the temperatures are below the predetermined temperature values.

Also, when the temperature sensor 282 a indicates that the temperature in the water flow has exceed a predetermined temperature value, the burner 222 is stopped, but the exhaust fan 246 and the heat pump 250 continues to work until a little bit higher temperature has been reached, or if the temperature falls, the burner 222 starts again. The temperature sensor 282 d in the exhaust chamber 244 prevents the burner 222 becoming active as long as the temperature is higher than the predetermined temperature value. A circulation pump in the heat pump 250 works continuously as long as the heat pump 250 is switched on.

Furthermore, when the temperature sensor 282 c recognizes that a temperature of the preheated incoming air flow exceeds a predetermined temperature value during the occurring spontaneous process between the moisture on the channel surfaces and the flue gas particles, the burner 222 is stopped. The process continues in the second channels although the burner is switched off and when the temperature sensor 282 c determines that the temperature of the preheated incoming air flow falls below another predetermined temperature value, the burner 222 is started again.

Even if the heat pump 250, the exhaust fan 246, and the boiler 220 are started in sequence one after the other, when an energy demand grows, the most favourable operation conditions are achieved. In connection with the boiler 220 and the heat pump 250 with heating by water, the water systems of the boiler 220 and the heat pump 250 are interconnected in sequence for obtaining a higher outgoing water temperature from the arrangement 200. The combustion air flow of the burner 222, which comprises room air, is also condensing dried by the heat pump 250, whereby no condensation occurs except a moisture in the fresh air introduced through the channel 242 in the proximity of the evaporator 254 in the heat pump 250, where pure condensation water can be collected and removed, or in the heat exchanger 240.

The invention has been now explained above with reference to the aforesaid embodiments and the several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the spirit and scope of the invention thought and the following patent claims. 

1-8. (canceled)
 9. A method for providing heat comprises preheating an incoming air flow from outside an apparatus (210) in a first channel of a heat exchanger (240) by means of a flow in a second channel of the heat exchanger, transferring the flow from the second channel of the heat exchanger outside the apparatus through an exhaust channel (248 a), providing heat by means of the preheated incoming air flow in a heat pump (250), and transferring in a transfer channel (270) a flue gas flow provided by a burner (222) to the second channel of the heat exchanger, wherein the method comprises receiving in the transfer channel a part of the exhausted flow from the exhaust channel and controlling a flow of the flue gas flow and the received part of the exhausted flow in the transfer channel so that moisture in the flue gas flow and the received part of the exhausted flow condenses on a surface of the second channel of the heat exchanger and reacts with flue gas particles of the flue gas flow when the flow of the flue gas flow and the received part of the exhausted flow interacts with the incoming air flow in the first channel of the heat exchanger increasing the preheating of the incoming air flow.
 10. The method of claim 9, wherein the method further comprises mixing the flue gas flow and the received part of the exhausted flow in the transfer channel.
 11. The method of claim 9, wherein the method further comprises providing a mixture comprising the flue gas flow and the received part of the exhausted flow in a condense chamber (272) of the transfer channel near a dew point of the mixture comprising the flue gas flow and the received part of the exhausted flow before transferring the mixture comprising the flue gas flow and the received part of the exhausted flow into the second channel of the heat exchanger.
 12. The method of claim 9, wherein the method comprises preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible by controlling a flow velocity of the mixture comprising the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger.
 13. The method of claim 9, wherein the method further comprises preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible by providing a tapered channel part in the second channel of the heat exchanger.
 14. The method of claim 9, wherein the method further comprises guiding the incoming air flow in the first channel of the heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flow in the second channel of the heat exchanger to flow opposite directions in the heat exchanger by means of a counter current heat exchanger (240).
 15. The method of claim 9, wherein a control unit (280) of the apparatus is capable of controlling an exhaust fan (246) and the burner of a boiler (220) when the apparatus is connected to an exhaust channel (248 b, 248 c) of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor (282 a, 282 b, 282 c, 282 d, 282 e) and a pressure sensor (284).
 16. An apparatus (210) for providing heat being configured to perform the method of claim 9, the apparatus comprises a heat exchanger (240) for preheating an incoming air flow from outside the apparatus in a first channel of the heat exchanger by means of a flow in a second channel of the heat exchanger, an exhaust channel (248 a) for transferring the flow from the second channel of the heat exchanger outside the apparatus, a heat pump (250) for providing heat by means of the preheated incoming air flow, a transfer channel (270) for transferring a flue gas flow provided by a burner (222) to the second channel of the heat exchanger and for receiving in the transfer channel a part of the exhausted flow from the exhaust channel, and control means (280) for controlling a flow of the flue gas flow and the received part of the exhausted flow in the transfer channel so that moisture in the flue gas flow and the received part of the exhausted flow condenses on a surface of the second channel of the heat exchanger and reacts with flue gas particles of the flue gas flow when the flow of the flue gas flow and the received part of the exhausted flow interacts with the incoming air flow in the first channel of the heat exchanger increasing the preheating of the incoming air flow.
 17. The method of claim 10, wherein the method further comprises providing a mixture comprising the flue gas flow and the received part of the exhausted flow in a condense chamber (272) of the transfer channel near a dew point of the mixture comprising the flue gas flow and the received part of the exhausted flow before transferring the mixture comprising the flue gas flow and the received part of the exhausted flow into the second channel of the heat exchanger.
 18. The method of claim 10, wherein the method comprises preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible by controlling a flow velocity of the mixture comprising the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger.
 19. The method of claim 11, wherein the method comprises preventing the condensed moisture to flow away from the second channel of the heat exchanger because of gravity so that the heat productive reaction between the condensed moisture and the flue gas particles is possible by controlling a flow velocity of the mixture comprising the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger.
 20. The method of claim 10, wherein the method further comprises guiding the incoming air flow in the first channel of the heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger to flow opposite directions in the heat exchanger by means of a counter current heat exchanger (240).
 21. The method of claim 11, wherein the method further comprises guiding the incoming air flow in the first channel of the heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger to flow opposite directions in the heat exchanger by means of a counter current heat exchanger (240).
 22. The method of claim 12, wherein the method further comprises guiding the incoming air flow in the first channel of the heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger to flow opposite directions in the heat exchanger by means of a counter current heat exchanger (240).
 23. The method of claim 13, wherein the method further comprises guiding the incoming air flow in the first channel of the heat exchanger and the mixture of the flue gas flow and the received part of the exhausted flowing the second channel of the heat exchanger to flow opposite directions in the heat exchanger by means of a counter current heat exchanger (240).
 24. The method of claim 10, wherein a control unit (280) of the apparatuses capable of controlling an exhaust fan (246) and the burner of a boiler (220) when the apparatus is connected to an exhaust channel (248 b, 248 c) of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor (282 a, 282 b, 282 c, 282 d, 282 e) and a pressure sensor (284).
 25. The method of claim 11, wherein a control unit (280) of the apparatuses capable of controlling an exhaust fan (246) and the burner of a boiler (220) when the apparatus is connected to an exhaust channel (248 b, 248 c) of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor (282 a, 282 b, 282 c, 282 d, 282 e) and a pressure sensor (284).
 26. The method of claim 12, wherein a control unit (280) of the apparatuses capable of controlling an exhaust fan (246) and the burner of a boiler (220) when the apparatus is connected to an exhaust channel (248 b, 248 c) of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor (282 a, 282 b, 282 c, 282 d, 282 e) and a pressure sensor (284).
 27. The method of claim 13, wherein a control unit (280) of the apparatuses capable of controlling an exhaust fan (246) and the burner of a boiler (220) when the apparatus is connected to an exhaust channel (248 b, 248 c) of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor (282 a, 282 b, 282 c, 282 d, 282 e) and a pressure sensor (284).
 28. The method of claim 14, wherein a control unit (280) of the apparatuses capable of controlling an exhaust fan (246) and the burner of a boiler (220) when the apparatus is connected to an exhaust channel (248 b, 248 c) of the boiler through the exhaust channel of the apparatus and the transfer channel of the apparatus by means of a temperature sensor (282 a, 282 b, 282 c, 282 d, 282 e) and a pressure sensor (284). 